Background: The effect of testosterone on the prostate gland is an unresolved question. The prostate saturation model is a recent hypothesis explaining that the stimulation of prostate tissue by testosterone is limited to a certain level of testosterone due to the limited number of androgen receptors. However, data from the Thai patients related to this issue are still lacking and need to be explored.

Objective: To investigate prostate changes after testosterone replacement therapy (TRT).

Materials and Methods: A retrospective study including testosterone-deficient patients who had TRT between 2011 and 2017 at Ramathibodi Hospital was conducted. The change in prostate-specific antigen (PSA) levels before and after TRT, or after a 1-year observation, was measured and analyzed as the primary objective. As a secondary objective, the authors measured and evaluated normal PSA velocity (PSAV) in the patients after TRT.

Results: One hundred eleven testosterone deficient patients were included for analysis. The mean age was 62 years old. The baseline testosterone level and PSA level at the beginning were 247 ng/dL and 1.16 ng/mL, respectively. After undergoing TRT for one year, the results showed that the testosterone and the PSA levels were 307 ng/dL and 1.46 ng/mL, respectively. In addition, the subgroup analysis illustrated that patients who had low baseline testosterone levels such as 247 ng/dL or less, had significant increase of PSA level after treatment. However, when the baseline testosterone level was more than 247 ng/dL, the PSA levels were steady after treatment. For the secondary-objective results, the PSAV of the testosterone deficiency patients after TRT was 0.3 ng/mL/year.

Conclusion: The evidence clearly indicates that TRT significantly increased the serum testosterone level. However, it had a limited effect on PSA change. The present study results supported the hypothesis of the prostate saturation model. The authors believe that a testosterone level of 247 ng/dL can saturate all androgen receptors in the prostate gland and no longer increase prostate stimulation.

Keywords: Prostate-specific antigen; Prostate cancer; Testosterone replacement Therapy; Prostate saturation

DOI: doi.org/10.35755/jmedassocthai.2021.09.12630

Received 16 February 2021 | Revised 7 April 2021 | Accepted 20 April 2021